264 
LIFE AND HER CHILDREN. 
leaves them to float. In a very short time the eggs 
are hatched and the young grubs swim briskly about, 
whirling round some tufts of hair which STOW on 
o o 
their mouths, and so driving microscopic animals and 
plants down their throats. Curiously enough they 
Fig. 90. 
Life of a Gnat. 
g, Grub breathing air through the tube /; /, pupa breathing air 
through two tubes t in the back ; , floating boat formed of the pupa 
skin ; , gnat rising out of it ; above the perfect gnat is on the wing. 
These figures are all magnified to give clearness. 
all swim head downwards and tail upwards (^ Fig. 
90), and the secret of this is that they are air-breath- 
ing animals and have a small tube at the end of their 
tail, which they thrust above water to take in air. 
This goes on for about a fortnight, when, after they 
